Theoretically… All (microbial) contaminants can be eliminated from plant tissue cultures by one or more antibiotics. In reality… This is seldom possible. No substitute for careful, aseptic work. Last resort when conventional techniques fail.

Antibiotic effectiveness can be affected by: • pH of medium – e.g., some are more effective at alkaline pH’s • Ion concentration of medium – high cation concentration can reduce effectiveness of some antibiotics Many antibiotics have short solution stability: • e.g., the Penicillin group → 24-48 hr at room temp. Phytotoxicity varies: • Between plant species • Between genotypes within a species • Between plant parts – organs vs. intact plant
24 May 2004 2004 WORLD CONGRESS on In Vitro Biology

• Mixture of sulfates of Streptomyces fradiae. • Water Soluble. • Solution Stability:
– Stable at room temperature. – 5° C for long term storage, yields some color change. Maximum of two years. – Protect from light.

• Since most microbial contaminants are unknowns, and, • Since microorganisms have different sensitivities to antibiotics it is difficult to specifically target microbial contaminants. • Unfortunately, it is common practice to use the “spray and pray” technique for antibiotic application… Best to check the literature first. • Broad-spectrum biocides frequently have bacteristatic/ fungistatic activity… continuous use may be required to control contaminants.
24 May 2004 2004 WORLD CONGRESS on In Vitro Biology